Inkjet printing mechanisms use cartridges, often called xe2x80x9cpens,xe2x80x9d which eject drops of liquid colorant, referred to generally herein as xe2x80x9cink,xe2x80x9d onto a page. Each pen has a printhead formed with very small nozzles through which the ink drops are fired. To print an image, the printhead is propelled back and forth across the page, ejecting drops of ink in a desired pattern as it moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as those using piezo-electric or thermal printhead technology. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481. In a thermal system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heater elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the page, the ink is expelled in a pattern on the print media to form a desired image (e.g., picture, chart or text).
To clean and protect the printhead, typically a xe2x80x9cservice stationxe2x80x9d mechanism is supported by the printer chassis so the printhead can be moved over the station for maintenance. For storage, or during non-printing periods, the service stations usually include a capping system which substantially seals the printhead nozzles from contaminants and drying. Some caps are also designed to facilitate priming, such as by being connected to a pumping unit that draws a vacuum on the printhead. During operation, clogs in the printhead are periodically cleared by firing a number of drops of ink through each of the nozzles in a process known as xe2x80x9cspitting,xe2x80x9d with the waste ink being collected in a xe2x80x9cspittoonxe2x80x9d reservoir portion of the service station. After spitting, uncapping, or occasionally during printing, most service stations have an elastomeric wiper that wipes the printhead surface to remove ink residue, as well as any paper dust or other debris that has collected on the printhead. The wiping action is usually achieved through relative motion of the printhead and wiper, for instance by moving the printhead across the wiper, by moving the wiper across the printhead, or by moving both the printhead and the wiper.
To improve the clarity and contrast of the printed image, recent research has focused on improving the ink itself. To provide quicker, more waterfast printing with darker blacks and more vivid colors, pigment-based inks have been developed. These pigment-based inks have a higher solid content than the earlier dye-based inks, which results in a higher optical density for the new inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to form high quality images on readily available and economical plain paper, as well as on recently developed specialty coated papers, transparencies, fabric and other media.
Due to the different natures of their compounds, pigment based inks and dye based inks have different servicing requirements, particularly when purging or xe2x80x9cspittingxe2x80x9d the printheads in a service station spittoon. Much research has been conducted over the past few years concerning the servicing of pigment based inks, for instance as described in U.S. Pat. Nos. 5,617,124; 6,082,848; 5,742,303; 5,980,018; 6,132,026; and 6,050,671, all currently assigned to the Hewlett-Packard Company, the present assignee of the technology disclosed herein; however, relatively few advances have been made in spittoons for dye based inks. One recent dye based ink spittoon having a fibrous liner of a polyester material was first commercially available in the Hewlett-Packard Company""s Professional Series 2000C color inkjet printer. This earlier fibrous ink absorber was very flexible and dimensionally imprecise, leading to difficulties in assembly and quality control. One solution to this fibrous absorber was a porous plastic ink absorber, made of a sintered polyethylene foam which could be molded into a rigid part. Unfortunately, this porous plastic absorber had a limited thickness and void volume, so less ink could be absorbed by the finished product. Moreover, the porous plastic absorber was very stiff and brittle, requiring tighter tolerances for mating parts, and was typically more expensive to manufacture than a fibrous absorber. Thus, a need existed for a dye based ink absorber, which could be easily assembled into a spittoon, and which maintained tight dimensional tolerances without adversely impacting other components in the system.